1. Field of the Invention
The present invention relates to a measuring technique of the earth's natural magnetism, and it particularly relates to a terrestrial magnetism detecting sensor which corrects the error encountered in azimuth calculation, and also relates to an azimuth measuring method thereof.
2. Description of the Related Art
The terrestrial magnetism detecting sensor is utilized to measure the orientation of an observation spot. The terrestrial magnetism detecting sensor also simply referred to as a magnetic sensor or a terrestrial magnetic sensor is placed on a horizontal plane at the observation spot, and detects biaxial or two-axis components of a terrestrial magnetic vector in the horizontal plane. The magnetic bearing is calculated based on the two axis components detected by the terrestrial magnetism detecting sensor. The terrestrial magnetism detecting sensor is used in the navigation system employed in an automobile, and is put on the market after certain calibration procedure has been performed to correct the magnetic effect.
On the other hand, it is widely prevalent that the map data are displayed in the cellular phone and other mobile terminals. In the light of this current situation, the applicant of the present invention first propose that the terrestrial magnetic sensor be built into portable equipment such as the cellular phone and mobile terminal, and came to recognize the following objects in the course of examining the realization of his proposal. Namely, the portable equipment may be held at any position depending on the posture of an owner of the portable equipment or how it is held by the owner, so that the direction of the portable equipment is not stabilized and constantly changes. Thus, the terrestrial magnetic sensor equipped in the portable equipment may be inclined by any possible tilt angle with respect to the horizontal position, and its tilt angle may constantly fluctuate. Therefore, under such a usage environment, besides the removal of the static magnetic effect as described above, an effect due to the change of the posture and holding position need be eliminated so that detection signals of the terrestrial magnetic vector can be automatically corrected.